1. Field of the Invention
The present invention relates, in general, to seats, and more specifically, to adjusters for vehicle seats.
Seat adjusters are used on the front seats of automotive vehicles to provide selective horizontal fore and aft movement of the seat to accommodate occupants, particularly drivers, of different size and height as well as to provide a comfortable seating position to suit each driver's preference. Such seat adjusters typically include a support frame which is connected to and supports a seat bottom and/or a seat back of a vehicle seat. A pair of spaced upper tracks are connected to the support frame and are each, in turn, slidably mounted in one of a pair of lower tracks which are anchored to the vehicle floor. A releasable lock mechanism is employed with such seat adjusters to lock the upper track, the support frame and the seat in any desired horizontal fore and aft position. The adjustable lock mechanism must provide a structure that ensures complete locking of the seat even when the seat is between predetermined horizontal fore and aft positions. Misalignment of the lower tracks and variances in tolerances may cause one upper track of the seat adjuster to lock while the other upper track is between predetermined horizontal fore and aft positions. The adjustable lock mechanism must ensure that the other upper track will lock upon minimal sliding of the seat in the horizontal fore and aft direction. Therefore, it would be desirable to provide a low inertia lock mechanism that quickly locks the upper track upon horizontal fore and aft movement of the seat when the lock mechanism is between predetermined horizontal fore and aft positions.
The lock mechanism must be strong enough to hold the upper tracks and seat in a fixed horizontal position under loads acting on the seat during a collision to prevent injury to the occupant. Thus, the weight and size of the seat adjuster components are selected to provide a maximum amount of strength to resist any movement of the seat adjuster and the seat and to securely anchor the seat adjuster to the floor under high impact forces transmitted to the seat from the occupant during a vehicle collision. Thus, the individual tracks, the seat support frame and the track anchors are made of stronger materials and in greater thicknesses and dimensions to provide the requisite amount of strength. Although this adds cost and weight to the seat, such efforts are considered essential to provide adequate strength to a seat to resist movement during a vehicle collision.
A recent trend in vehicle seat design is to incorporate the seat as part of the occupant protection or safety system. Test results embodied in Federal Motor Vehicle Safety Standards 208 and 210 require that seat belts and their anchorages withstand loads of 1500 to 3000 pounds without failure. If any seat belt anchor is mounted to the seat structure, the seat structure must also withstand such loads as well. The outboard (adjacent the door) upper, shoulder seat belt and lower, lap seat belt and their anchors should withstand a load of 1500 pounds and the inboard (adjacent the vehicle centerline) lap seat belt point should withstand a load of 3000 pounds.
However, despite the added load the seat belts transfer to a vehicle seat frame, it is still desirable to mount the seat belt buckle assembly directly to the seat track assembly since adjustment of the seat by an occupant would not require readjustment of the seat belt. Further, integration of the seat belt buckle mounting to the seat track assembly enables the seat belt and seat belt buckle assembly to be designed as a unitary structure so as to simplify vehicle floor pan construction and installation at the vehicle assembly plant.
At the same time, increased emphasis on fuel economy and the imposition of higher federally mandated fuel economy standards necessitate vehicle weight reduction. This makes it desirable to reduce the weight of the vehicle seat, but such weight reduction is directly opposed to the high strength requirements noted above.
Also, increased competition has led to the need to reduce cost and increase efficiency in both parts and labor. Therefore, it is desirable to design a vehicle seat adjuster that reduces the number of parts to the assembly while reducing the amount of labor required to assemble these parts.
Thus, it would be desirable to provide a vehicle seat adjuster with a low inertia lock mechanism that, when between predetermined horizontal fore and aft positions will quickly engage to lock the vehicle seat adjuster upon horizontal fore and aft movement of the seat. It would be desirable to provide a vehicle seat adjuster which meets the need for high strength to prevent seat and seat belt buckle anchorage movements or track separation under collision impact loads. Furthermore, it would be desirable to provide a vehicle seat adjuster which allows easy fore and aft adjustment, and, at the same time, minimizing weight and manufacturing cost. In addition, it would be desirable to provide a vehicle seat adjuster that provides a minimum amount of assembled parts and fasteners in order to reduce labor and material costs.